It is generally accepted that fresh human sweat is odorless, and that the smell of sweat is generated by microorganism colonizing the human skin and particularly the axilla. The smell thus generated from human sweat is considered characteristic in the sense that upon smelling such scent it is immediately clear that the scent indicates human sweat. The smell is widely and according to the present invention considered to be a malodour and can be very pronounced.
It has thus been tried for ages to inhibit the generation of sweat malodour to reduce the malodour or to mask it. In the context of the present invention, “inhibition” designates all means to prevent the formation of sweat malodour from human sweat, including means for slowing down such malodour generation. “Reduction” refers to means for treating the constituents of sweat malodour to render them less intense, e.g. by binding to and immobilizing on a matrix. “Masking” designates those means and efforts intended to affect the human perception of sweat malodour, e.g. by overwhelming a human nose with other, more intense and less malodorous scents, or otherwise reducing or impairing the ability of the human olfactory system to detect one or more malodorous compounds of sweat malodour.
It is desirable to inhibit the formation of sweat malodour and not only to reduce or mask such malodour. One way frequently tried is the application of antiperspirants to human axilla to prevent the formation of sweat. The reasoning is that when no sweat is formed, no sweat malodour will be generated. However, there are concerns that such influencing of human physiological processes may not be sustainable or lead to undesired side effects. In the context of the present invention “inhibitors” therefore are only those substances which are effective to slow down or prevent the formation of one or more constituent of sweat malodour from human sweat other than any relying predominant by on the suppression of secret formation.
There is thus a general need to find effective inhibitors of sweat malodour generation. The search for such inhibitors is hampered by the fact that little is known about the actual formation of sweat malodour, particularly the physiological processes of microorganisms responsible for malodour generation. Further, there is a lack of standardized procedures to compare efficacy of potential malodour generation inhibitors.
Document EP 1 387 891 (also published as WO 02/092024 A2) discloses an isolated N-alpha-acyl-glutamine-aminoacylase reportedly involved in the transformation of odorless precursor compounds found in sweat into malodorous fatty acids. The document further describes the application of this enzyme in high throughput screening for inhibitors.
A disadvantage of the enzyme disclosed in the aforementioned European patent document and correspondingly also of the test system described therein is that the enzyme requires as a cofactor a zinc ion and is thus easily affected by the presence of chelating agents. However, zinc chelating agents like EDTA are not efficient for inhibiting the generation of human sweat malodour when applied to human sweat in vivo. Thus, the test system requires great care when preparing the reagents used therein, and potential inhibitors identified by the test system have to be reanalysed to rule out that their malodour inhibitory effect as determined by the test system is not merely a result of their interference with zinc ions.
It was therefore a problem of the present invention to provide a test system for reproducing a representative pathway of sweat malodour generation without being dependent upon the presence of zinc ions.